Watchtower holds the possition that Jesus Christ at the last supper, had the celebration of the Jewish Passover, and that the bread He shared with the disciples was unleavened bread.
The Gospel account it might be misleading at first, and lead to a wrong conclusion like WT does. With a close examination what happened regarding Jesus Last Supper, and compare the Old Testament accounts of the Passover and the Gospels account, the outcome is completely different.
Mark 14:12 shows that the Last Supper occured the day before the unleavened feast, and at Mark 14:22 Jesus here cut the Bread and share it. In the Bible when the bread is unleavened it is specifying this. And in this case Jesus shared a normal bread. In the Greek testament it makes it clear when it says Arton-bread and azymos artos-unleavened bread.
Then He was arrested at the garden of Gesthemany Mark 14:26-43 early Friday(Paraskevi)morning and He was delivered by the Scribes and Pharisees to the Roman Governor.
At the same morning the Priests did not entered at the Roman Praitory in order not to get defiled, since the celebration of the Passover was starting from Friday evening to Saturnday-or Sabath to be more correct. Friday(Parskevi)was the eve of the Jewish Passover and eating unleavened bread, lamb, before that was forbidden by the law. - Exodus 12
So Jesus did not celebrate the Jewish Passover, but the New Govenant that He set one night before He was crucified at the beggining of the Jewish Passover.-John 18:28, 19:31. It is obvious that Apostle John give us the day Jesus celabrated the New Passover a day before the Jewish. Also Jesus had wine at the table, while the Jewish Passover did not included wine.- Exodus 12
Simon from Kyreni was engaged to help Jesus to carry the Cross. - Mark 15:21, and he was coming from the work at the fields. So if the celebretion of the Passover has started, Simon wouldn't go and work at the fields since it was forbidden by the Mosaic Law
Joseph of Arimathea went to the shops and bought the linen cloth for Jesus burrial - Mark 15:46. So there was NO WAY to have open shops if the Passover has began
This is the Biblical account regarding Jesus Last Supper and the Bread. This is why the Orthodox Faith ever since the early days of the Apostolic Church has kept the faith as it was delivered by Jesus and the Apostles.
Using unleavened bread at the Eucharist it is heretic and it goes back with the Apollinaris heretic view regarding the Bread